Sealed type electrically driven compressor

ABSTRACT

A hermetic electric compressor is capable of efficiently pumping up a necessary amount of lubricating oil even at low-speed rotation and has a simple constitution to provide an excellent workablity in assembling. The hermetic electric compressor includes an oil pump. The oil pump includes (i) a slanting channel formed in the lower portion of a main shaft and slanting from the lower portion to the upper portion thereof outwardly, (ii) a throttle formed at the bottom end of the main shaft and having an inlet port of diameter smaller than the section of the slanting channel at the center thereof, and (iii) a lower communicating passage for providing a communication between the bottom end of a spiral groove and the slanting channel. This constitution is capable of effectively lift the head of the lubricating oil.

FIELD OF THE INVENTION

The present invention relates to a hermetic electric compressor for usein freezing and refrigerating equipment or a room air-conditioner. Itmore particularly relates to an oiling and lubricating system forsupplying lubricating oil reserved in a hermetic shell to rotating andsliding parts in the hermetic electric compressor by a centrifugal forceof a rotation of a crankshaft.

BACKGROUND OF THE INVENTION

Recently, there has been a strong demand for reduction in powerconsumptions and noise in a hermetic electric compressor for use in adomestic freezer and refrigerator or a room air-conditioner. For areduction in power consumptions and a noise, an inverter-drivencompressor is operated at a lower rotational speed (e.g. approx. 1,800revolutions per minute (rpm) for a domestic refrigerator).

On the other hand, many lubricating oil pump systems for a hermeticelectric compressor utilize a centrifugal force resulting from arotation of a crankshaft because a lubricating oil reserved in thebottom of a hermetic shell is pumped up to upper sliding parts However,because the centrifugal force is proportional to the square of arotational speed of a crankshaft, a power of pumping up oils is smalleras a rotational speed is lower. This causes a serious problem in theoperation at a lower rotational speed.

A prior art is described hereinafter.

One of conventional hermetic electric compressors is disclosed in theJapanese Patent Unexamined Publication No. 1987-44108. FIG. 14 shows asectional view of the conventional hermetic electric compressor. Withreference to FIG. 14, a compressor body 500 is housed in a hermeticshell 501. In the hermetic shell 501, a frame 502 is disposed in thecenter, an electric motor 503 in the lower portion, and a compressingmechanism 504 in the upper portion. A crankshaft 505 penetrates througha bearing 506 of the frame 502. While the outer diameter portion of thecrankshaft 505 is fixed to rotor 507 of the electric motor 503, aneccentric crankshaft 508 is engaged with a slider 510 of a piston 509 inthe compressing mechanism 504 to perform a well-known compressingaction.

Inside of the crankshaft 505, a slanting channel 511 having a relativelysmall diameter extends from the bottom end of the crankshaft 505 to thebottom end of a bearing 506. The slanting channel is opened to the outerperiphery of the crankshaft 505 by a first lateral hole 512. A spiralgroove 513 is formed on a portion of the crankshaft 505 inside of thebearing 506. The bottom end of the spiral groove is in communicationwith the lateral hole 512. At the top end of the spiral groove, thebottom end of a longitudinal hole 514 provided in an eccentric shaft 508is opened to a thrust bearing sliding on a surface 515. At the sametime, the bottom end of the longitudinal hole 514 intersects a secondlateral hole 516. In other words, the crankshaft 505 is constituted sothat the holes 512 and 516 are opened directly to the outer surface ofthe crankshaft 505. Additionally, at a bottom end 517 of the crankshaft505, the slanting channel 511 is opened to a lubricating oil 518.

FIG. 15 is a detail sectional view of the bottom end 517 of thecrankshaft 505 immersed in the lubricating oil 518. The lubricating oil518 in the slanting channel 511 is formed into a free surface shapedlike a parabola by a centrifugal force resulting from a rotation of thecrankshaft 505. At this time, an ascending current 519 of thelubricating oil 518 sucked through the opening surface of the slantingchannel 511 at the bottom end 517 of the crankshaft 505 is separatedinto two branches 520 and 521. A branch 520 is moved upwardly by thecentrifugal force resulting from the rotation of the crankshaft 505.Another branch 521 slips in the vicinity of the bottom end of theslanting channel 511 and escapes through the opening surface of theslanting channel 511 out of the slanting channel 511. This branch 521merges with the ascending current 519 sucked through the opening surfaceof the slanting channel 511 and flows into the slanting channel 511again to form a short circuit.

In the constitution of such a prior art, the lubricating oil in theslanting channel 511 that directly extends from the bottom end of thecrankshaft 505 diagonally to the top is immediately decentered by thecentrifugal force only on the inner surface of the slanting channel 511on the outer peripheral side, in a position slightly above the oil levelof the lubricating oil 518 reserved in the lower portion of thecompressor 500. Therefore, a force of lifting the lubricating oil isexcellent. However, the ascending current 519 shown by the arrow, i.e.the lubricating oil that has been sucked through the opening surface ofthe slanting channel 511 at the bottom end of the crankshaft 505, isseparated into the branches 520 and 521 each shown by the arrow. Thebranch 520 is moved upwardly by the centrifugal force. The branch 521flows through the opening surface of the slanting channel 511 out of theslanting channel 511. This branch 521 merges with the ascending current519 sucked through the opening surface of the slanting channel 511 andflows into the slanting channel 511 again to repeat short circuits.Repeating the short circuits is a major factor of the loss in the amountof the lubricating oil 518 flowing into the slanting channel 511.Further, because the centrifugal force is smaller at a lower rotationalspeed of the crankshaft 505, the rate of the branch 521 flowing out ofthe slanting channel 511 increases. This causes a drawback of deliveringan insufficient amount of the lubricating oil to the sliding part in theupper portion.

Another hermetic electric compressor constituted to increase acentrifugal force for sucking an oil is disclosed in U.S. Pat. No.5,707,220. However, this prior art has a complicated path of lubricatingoil and a complicated constitution, and thus requires a large number ofcomponents. This causes problems of unstable supply of a lubricating oiland poor workablity in assembling.

Still another conventional hermetic electric compressor is disclosed inWO00/01949 Publication. This compressor employs a mechanical oil pumpsystem in which the viscosity effect of lubricating oil pumps up alubricating oil along a spiral groove between a stator having the spiralgroove in the outer peripheral, surface thereof and a rotating sleeve.This system is highly reliable in ensuring an amount of supplied oil ina low-speed range (1,200 to 1,800 rpm). However, the constitution isextremely complicated and requires a larger number of components incomparison with an oil pump system using a centrifugal force. Therefore,this mechanical oil pump system has drawbacks of an expensiveness and apoor workability in assembling.

The present invention solves these conventional problems and aims toprovide a simple lubricating oil pump system for a hermetic electriccompressor that is capable of efficiently pumping up lubricating oileven at a low-speed rotation and has an excellent workablity inassembling.

DISCLOSURE OF THE INVENTION

A hermetic electric compressor of the present invention has thefollowing constitutions: an electric motor including a stator and arotor; a compressing element for compressing refrigerant by a rotationof a crankshaft fixed to the rotor of the electric motor; and a hermeticshell for housing the electric motor and the compressing element andincluding a reservoir for storaging a lubricating oil. The crankshaft isconsisted of at least a main crankshaft, and a eccentric crankshaft fordriving the compressing element. The hermetic electric compressorfurther includes an oil pump for supplying the lubricating oil in thesump to the main crankshaft and the eccentric crankshaft by a rotationof the crankshaft. The oil pump is constituted to have (i) a slantingchannel inside of the main crankshaft that has a predetermined lengthfrom the bottom end of the main crankshaft immersed in the sump andinclines with respect to the center axis of the main crankshaft, (ii) athrottle provided at the bottom end of the main crankshaft and having across-sectional area smaller than that of the slanting channel, (iii) acommunicating passage provided at the top end of the slanting channel,(iv) a spiral groove in communication with the communicating passage,provided in the outer periphery of the main crankshaft, and (v) athrough hole in communication with the spiral groove, provided in theeccentric crankshaft.

Because of this constitution, the centrifugal force resulting fromrotation of the crankshaft is exerted on the lubricating oil at thebottom end of the main crankshaft surrounded by the throttle and thethrottle receives the downward force. This increases the upward forceresulting from the centrifugal force and moves the lubricating oilupwardly in the slanting channel. Further, because the incline of theslanting channel effectively lifts the head of the lubricating oil, aforce of delivering a large amount of oil can be obtained.

Additionally, because the crankshaft is operated at rotational speedsranging from 1,200 to 1,800 rpm, the power input of the compressor isminimized. Together with a stable lubrication, an operation at the lowpower consumption is allowed.

Further, the ratio of the distance from the most bottom end of the maincrankshaft to the center of the communicating passage to the diameter ofthe main crankshaft in the area housing the slanting channel is set toE. The ratio of the maximum length from the center axis of the maincrankshaft to the outer diameter of the slanting channel to the diameterof the main crankshaft is set to F. The relation between the ratios Eand F is set to be shown by the following equation:F≧0.166E ²−0.683E+1.44

Setting the ratios to satisfy the above equation optimizes thedimensions of the oil pump and thus provides an oil pump maximizing theutilization of the centrifugal force. Thus, a delivering force of alarge amount oil can be obtained even in operation at a low speedrevolution.

As for the throttle, a disk-shaped cap is inserted in and engaged withthe bottom end of the main crankshaft. Thus, the material cost is lowand the throttle can be assembled without positioning the cap bymistake.

Additionally, the ratio of the diameter of the slanting channel to thediameter of the inlet port provided at the center of the throttle is setto 1:0.25 to 0.5. This provides an oil pump in which an amount ofsupplied oil can be changed in the range of high-speed operation whilethe amount of supplied oil in the range of low-speed operation is kept amaximum. Thus, an appropriate amount of supplied oil can be obtained inoperation at each rotational speed.

Further, a divider shaped like a flat plate is inserted in and engagedwith the slanting channel. The divider prevents oil from slipping in theslanting channel and ensures stable lubrication especially in operationat low rotational speeds.

The divider is shaped like a vertically symmetrical flat plate. Thedivider has a semi-circular notch in substantially the center at leastat the bottom end. The divider also has a press fit portion in which thewidth of almost the longitudinal center is larger than those of the topand bottom ends. The semi-circular notches provided at the both ends ofthe divider keeps the ratio of two divided openings of the inlet port inthe throttle unchanged even when the bottom end of the divider isdisplaced from the center of the throttle. Increasing the width of theportion in the vicinity of the longitudinal center allows the divider tobe inserted from any of the top and bottom ends thereof and prevents thedivider from curving, thus increasing the workablity in assembling.

Further, a step is provided in a position in the direction of the depthof the slanting channel from the bottom end thereof. The distance fromthe bottom end of the slanting channel to the step is equal to thelength of the divider. This constitution allows the slanting channel tobe manufactured at a plurality of processes and thus increases anaccuracy of finishing. Additionally, when the divider is inserted intothe slanting channel, the edge of the divider at the top end thereof isheld by the step in the slanting channel. This allows assembling withoutpositioning the divider by mistake.

Further, the compressor is constituted so that a conical portion isformed at the top end of the slanting channel and at least a part of thecommunicating passage intersects the conical portion. This constitutioncan thicken the portion of the crankshaft above the communicatingpassage and thus prevent a corrosion (a phenomenon of breakage at thebottom of a spiral groove developing into a large hole that occurs in athin portion) likely to occur in this portion.

Further, the compressor is provided a vent communicating passage forcommunication between the slanting channel and the outer peripheralsurface of the main crankshaft and opened to the space in the hermeticshell. This constitution increases the height from the oil level to thecenter of the vent communicating passage and thus decreases the amountof lubricating oil flowing out of the vent communicating passage. As aresult, the amount of lubricating oil to be pumped up can relatively beincreased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a hermetic electric compressor inaccordance with a first exemplary embodiment of the present invention.

FIG. 2 is a sectional view of an essential part of a crankshaft inaccordance with the first exemplary embodiment of the present invention.

FIG. 3 is a sectional view of an essential part of the crankshaft inaccordance with the first exemplary embodiment of the present invention,showing how the lubricating oil is pumped up.

FIG. 4 is a characteristic showing a relation between an amount ofsupplied oil and a ratio E by setting ratio a ratio F as a parameter.

FIG. 5 is a characteristic showing a relation between a ratio E and Fderived from FIG. 4.

FIG. 6 is a characteristic showing a relation between an operatingfrequency and an amount of supplied oil.

FIG. 7 is an enlarged sectional view of a lower portion of a maincrankshaft in accordance with a second exemplary embodiment of thepresent invention.

FIG. 8 is a characteristic showing a relation between an amount ofsupplied oil and a ratio G in accordance with the second exemplaryembodiment of the present invention.

FIG. 9 is an enlarged sectional view of a lower portion of a maincrankshaft in accordance with a third exemplary embodiment of thepresent invention.

FIG. 10 is a perspective view of a divider.

FIG. 11 is an enlarged sectional view of portion D of FIG. 9.

FIG. 12 is an enlarged sectional view of a top end portion of a slantingchannel in a main crankshaft in accordance with a fourth exemplaryembodiment of the present invention.

FIG. 13 is an enlarged sectional view of a bearing for a main crankshaftin accordance with a fifth exemplary embodiment of the presentinvention.

FIG. 14 is a sectional view of a conventional hermetic electriccompressor.

FIG. 15 is a sectional view of an essential part of the conventional howto pump up a lubricating oil shown in FIG. 14.

PREFERRED EMBODIMENTS OF THE INVENTION

Exemplary embodiments of the present invention are described hereinafterwith reference to the accompanying drawings.

First Exemplary Embodiment

FIG. 1 is a sectional view of a hermetic electric compressor inaccordance with the first exemplary embodiment of the present invention.FIG. 2 is a sectional view of an essential part of a crankshaft inaccordance with the first exemplary embodiment. FIG. 3 is a sectionalview of an essential part of the crankshaft in accordance with the firstexemplary embodiment, showing how a lubricating oil is pumped up.

A hermetic electric compressor body 1 is constituted to house anelectric motor 3 comprising a stator 3 a and a rotor 3 b, and acompressing unit 6 integrated a compressing mechanism 4 by a cylinderblock 5 in upper and lower hermetic shell 2. A main crankshaft 7 a of acrankshaft 7 is supported by a bearing 8 of a cylinder block 5. Coupledto an eccentric crankshaft 7 b in the upper portion of the crankshaft 7is a connecting rod 10. Coupled to the connecting rod 10 is a piston 13for sliding via a piston-pin 11 in a cylinder 12. A valve plate 14includes a suction port, suction valve, discharge port and dischargevalve (each not shown). A cylinder head 15 is partitioned to have asuction chamber and a discharge chamber (each not shown) inside thereof.The cylinder head 15 is coupled to a suction muffler 16. A lubricatingoil 30 is reserved in the bottom portion of a hermetic shell 2.

As shown in FIG. 2, a slanting channel 19 is bored in main crankshaft 7a. Additionally, at the bottom end of the slanting channel 19, athrottle 17 having a small radius inlet port 29 for sucking thelubricating oil 30 is provided. The slanting channel 19 is a passage fora lubricating oil 30 that is provided to incline with respect to thecenter axis of main crankshaft 7 a. The center of inlet port 29 in thethrottle 17 is placed at the center of of the slanting channel.

As shown in FIG. 1, the slanting channel 19 is bored so that the top endthereof reaches the lower portion of bearing 8 of the cylinder block 5.At the top end of the slanting channel 19, the slanting channel 19 isprovided in the proximity of the outer peripheral surface of maincrankshaft 7 a. As shown in FIGS. 1 and 2, a spiral groove 20 isprovided in the outer periphery of main crankshaft 7 a above theslanting channel 19. The spiral groove 20 is in communication with theslanting channel 19 at a lower communicating passage 21 provided at thetop end of the slanting channel 19. Further, at the top end of thespiral groove 20, an upper communicating passage 24 in communicationwith through-hole 23 in the eccentric crankshaft 7 b is provided.

As shown in FIG. 2, each numerical value in such a constitution isdefined as follows. Y is a diameter of the main crankshaft 7 a in thearea in which the slanting channel 19 is bored. H is a height from thebottom end of the main crankshaft 7 a to the center of a lowercommunicating passage 21. The ratio of the height H from the bottommostend of main crankshaft 7 a to the center of lower communicating passage21 to the diameter Y of main crankshaft 7 a is set to E (E=H/Y).Further. P is a radius of the main crankshaft 7 a, i.e. Y/2. R is amaximum length from the center axis of the main crankshaft 7 a to anouter diameter of the slanting channel 19. The ratio of the maximumlength R from the center axis of main crankshaft 7 a to the outerdiameter of slanting channel 19 to the radius P of main crankshaft 7 ais set to F (F=R/P).

Next, an operation of the hermetic electric compressor in thisconstitution is described.

FIG. 3 is a sectional view of an essential part of the bottom endportion of the main crankshaft 7 a, showing how the lubricating oil 30in the slanting channel 19 is pumped up when the crankshaft 7 rotates.By a centrifugal force resulting from a rotation of the crankshaft 7,the lubricating oil 30 in the slanting channel 9 is formed to a freesurface shaped like a parabola. A lubricating oil flow A through theinlet port 29 provided in the throttle 17 that is shown by the arrow isseparated into two branches B and C each shown by each arrow. The branchB is moved upwardly by the centrifugal force. The branch C slips alongthe inner surface of the slanting channel 19. This branch C reflectsfrom the inner surface of the throttle 17 and merges with the branch Bto repeat short circuits. However, a phenomenon of the lubricating oil30 that has flown into the slanting channel 19 once and flown out of theslanting channel 19, which is described in the prior art, can beavoided. Therefore, the loss in the amount of lubricating oil 30 flowinginto the slanting channel 19 can remarkably been inhibited. In otherwords, because the throttle 17 receives the downward force, the upwardforce is larger than that of the prior art, thereby increasing the forceof delivering the lubricating oil 30 upwardly in the slanting channel19.

FIG. 4 shows a relation between an amount of supplied oil and the ratioE (E=H/Y) using the crankshaft 7 having an equal outer diameter. E isthe ratio of height H from the bottommost end of main crankshaft 7 a tothe center of lower communicating passage 21 to diameter Y of maincrankshaft 7 a. At this time, the ratio F (F=R/P) is used as aparameter. F is the ratio of maximum length R from the center axis ofmain crankshaft 7 to the outer diameter of slanting channel 19 to radiusP of main crankshaft 7 a. In the shown results, the rotation of thecrankshaft 7 in operation is constant, i.e. 1,200 rpm. The lubricatingoil used is ester oil having a viscosity ranging from 10 to 15 mm²/sec.As obviously from FIG. 4, for any ratio F, a tendency of an amount ofsupplied oil to decrease with an increase of the ratio E is confirmed.In order to pump up the lubricating oil 30, it is a prerequisitecondition that the upward force resulting from the centrifugal forcethat is exerted on the lubricating oil 30 overcomes the downward forceresulting from gravity or a slip. At the smaller ratio E, the upwarddelivering force is stronger. FIG. 4 also shows a tendency of an amountof supplied oil to increase with an increase of the ratio F This isbecause the centrifugal force exerted on the lubricating oil 30 in theslanting channel 19 is larger at the larger ratio F Naturally, thedelivering force is stronger when the ratio F approximates to 1.

FIG. 4 also shows a lubrication limit line 40 a, i.e. 40 ml/min., as anexample in this embodiment. When the amount of lubricating oil 30supplied to the upper portion of the crankshaft 7 is under thelubrication limit line, a supply of lubricating oil 30 to the slidingpart is insufficient and thereby a wear and tear may occur.

FIG. 5 shows a relation between the ratio E and the ratio F based on theresults of FIG. 4 in which an amount of supplied oil of 40 ml/min. canbe ensured in operation at a rotation speed of 1,200 revolutions perminute (rpm). FIG. 5 shows a lubrication limit line 40 b above which anamount of supplied oil of 40 ml/min. can be ensured in operation at arotational speed of 1,200 rpm. The lubrication limit line 40 b isexpressed by Equation (2). On the other hand, there is a sufficientlubrication region 40 c above the lubrication limit line 40 b, in whichan amount of supplied oil not less than 40 ml/min. can be ensured. Thisregion is expressed by the Equation (1). Further, there is aninsufficient lubrication region 40 d below the lubrication limit line 40b, in which an amount of supplied oil is less than 40 ml/min. Thisregion is expressed by the Equation (3).F≧0.166E ²−0.683E+1.44  (1)F=0.166E ²−0.683E+1.44  (2)F<0.166E ²−0.683E+1.44  (3)

These results show that the compressor should be designed so that theratio E and F satisfy the Equation (1), in order to ensure an amount ofsupplied oil of 40 ml/min.

FIG. 6 is showing a correlation between the revolutions in operation andthe amount of supplied oil both in the prior art and the presentinvention, using the main crankshafts 7 a having an equal diameter. Now,as a dimension of the main crankshaft 7 a in the present invention, theratio E ranges 2 to 3, the ratio F ranges from 0.77 to 0.9, and theratio E and F satisfies the Equation (1). In FIG. 6, the revolutions inoperation is shown in an operating frequency. Multiplying an operatingfrequency in the Fig. by 60 gives the number of revolutions inoperation. As obviously from the Fig., the amount of supplied oil of thehermetic electric compressor of the present invention is larger thanthat of the prior art, in operation at any revolutions. In the presentinvention, an amount of supplied oil sufficient to lubricate the slidingpart can be ensured even in the range of low-speed operation (1,200 to1,800 rpm). Additionally, together with stable lubrication, theoperation at low rotational speeds can minimize the input of thecompressor, thereby realizing low power consumptions.

In this exemplary embodiment, the ratio E ranges from 2 to 3. When theratio E is smaller than 2, there is almost no allowance for the length(approx. 10 to 20 mm) to which the rotor 3 b is fitted in the lowerportion of the main crankshaft 7 b. Thus, this is not a realisticdesign. On the other hand, when the ratio E is larger than 3, the pumphead is too high to ensure a sufficient amount of supplied oil in therange of low-speed operation (1,200 to 1,800 rpm).

In this exemplary embodiment, the ratio F ranges from 0.77 to 0.9. Whenthe ratio F is smaller than 0.77, the centrifugal force to provide anoil delivering force cannot be obtained and a sufficient amount ofsupplied oil cannot be ensured in the range of low-speed operation(1,200 to 1,800 rpm). On the other hand, when the ratio F is larger than0.9, a thickness between the outer peripheral of the main crankshaft 7 aand the slanting channel 19 is smaller than 1 mm. Therefore, when acompressive load is imposed, chips or cracks may develop in the portionhaving a small thickness.

Consequently, in order to design a lubricating system of the crankshaft7 capable of performing compressing operation even in the low-speedoperation, it is desirable to set the ratio E to the range of 2 to 3,the ratio F to the range of 0.77 to 0.9, and use the Equation (1) as therelation between the ratio E and the ratio F.

Generally, a temperature of the compressing mechanism 4 comprising thepiston 13 and the cylinder 12 is higher than that of the lubricating oil30 scattered from the top end of the eccentric crankshaft 7 b ofcrankshaft 7. Therefore, in the first exemplary embodiment of thepresent invention, an amount of the lubricating oil 30 sprayed onto thecompressing mechanism 4 increases and thereby the cooling effect isfully exerted on the compressing mechanism 4. This inhibits a wear andtear of the surface of the sliding part and improves a reliability.Additionally, because a temperature rise of the gas sucked into thecompressing mechanism 4 is inhibited, the efficiency of the hermeticelectric compressor can be improved.

Second Exemplary Embodiment

FIG. 7 is an enlarged sectional view of a lower portion of a maincrankshaft in accordance with the second exemplary embodiment of thepresent invention.

As shown in FIG. 7, at the bottom end of the main crankshaft 7 a, anextended tubular part 18 and a throttle 17 are formed. The slantingchannel 19 serving as a passage for a lubricating oil is bored from atop end of the extended tubular part 18 so as to incline with respect tothe center axis of the main crankshaft 7 b. The internal diameter of theextended tubular part 18 is formed larger than the diameter of theslanting channel 19. A cap 31 shaped like a flat disk is inserted alongand engaged with the inner peripheral of the extended tubular part 18.The cap 31 is formed by punching an ordinary steel stock or the like,and has an inlet port 29 for sucking the lubricating oil 30 at thecenter thereof. The throttle 17 is a generic term including the extendedtubular part 18 and the cap 31 having the inlet port 29.

U is a diameter of the slanting channel 19. X is a diameter of the inletport 29 provided at the center of the throttle 17. The ratio of thediameter X to the diameter U of slanting channel 19 is set to G (G=X/U).

In the second exemplary embodiment of the present invention, a materialof the cap 31 is an ordinary steel stock represented by SS or SKmaterial. The cap 31 is shaped like a disk by punching the steel stock,and press-fitted along the inner periphery of the extended tubular part18. Thus, the cap 31 can be realized at low cost and with highworkability. Additionally, a step formed by a difference in a diameterbetween the extended tubular part 18 and the slanting channel 19 allowsa stable assembling without positioning misregistration of the cap 31when the cap 31 is press-fitted.

As for the material of cap 31, the same effect can be obtained by theuse of inexpensive non-ferrous metal, plastic material, or the like,instead of the ordinary steel stock.

Next, FIG. 8 shows the data obtained by measuring the correlationbetween an amount of supplied oil and the ratio G, using the crankshaftshaving an equal diameter. In the results of FIG. 8, the representativevalues under two operation conditions at rotational speeds of 1,200 rpmand 4,320 rpm, are shown with the ratio E set to 2.6 and the ratio F setto 0.82. The lubricating oil used is ester oil having a kineticviscosity ranging from 10 to 15 mm²/sec. A line 40 e shows a line alongwhich the ratio G is 0.25. A line 40 f shows a line along which theratio G is 0.5. This FIG. 8 shows that a maximum amount of supplied oilpoint exists within the region of the line 40 e along which the ratio Gis 0.25 to the line 40 f along which the ratio G is 0.5 at both of 1,200rpm and 4,320 rpm. Additionally, in operation at 1,200 rpm, there isalmost no difference in an amount of supplied oil when the ratio Granges from 0.25 to 0.5. On the contrary, in operation at 4,320 rpm, amaximum peak is obviously confirmed when the ratio G is approx. 0.43.

As a diameter of the inlet port 29 formed at the center of the throttle17 is larger, the amount of supplied oil decreases both in high-speedoperation and low-speed operation. The reason is why the capability ofreceiving the downward force generated by the centrifugal forcedecreases and the loss in the amount of the lubricating oil 30 flowinginto slanting channel 19 increases.

On the other hand, in the operation at 4,320 rpm, the amount of suppliedoil remarkably decreases as the ratio G is smaller than 0.43. The reasonis why the stronger centrifugal force in high-speed operation increasesthe force of delivering the lubricating oil 30 upwardly, and thus theamount of the lubricating oil 30 sucked through the inlet port 29 cannotfollow the amount of lubricating oil 30 to be lifted. Such a tendency ofthe amount of supplied oil to remarkably decrease with a decrease in theratio G is confirmed in an operation at rotational speeds more than3,000 rpm. On the contrary, the amount of lubricating oil 30 suckedthrough the inlet port 29 is relatively small in the range of low-speedoperation. Therefore, there is a wider range in which the amount oflubricating oil 30 sucked through the inlet port 29 can follow theamount of lubricating oil 30 to be lifted. Thus, it is considered thatsuch a range of the ratio G is wider in low-speed operation. Thephenomenon of an existence of the range of the ratio G in which anamount of supplied oil is flat in the range of low-speed operation isconfirmed at rotational speeds less than 1,800 rpm.

As described above, in the second exemplary embodiment of the presentinvention, the ratio of the diameter of the slanting channel 19 to thediameter of the inlet port 29 provided at the center of the throttle 17is 2.0 to 4.0. This constitution can provide an oil pump capable ofchanging an amount of supplied oil in the range of high-speed operationwhile maintaining the amount of supplied oil in the range of low-speedoperation maximum. Especially when a remarkably large amount of thelubricating oil 30 is discharged from the top end face of the eccentriccrankshaft 7 b in the upper portion of the crankshaft 7 in the range ofhigh-speed operation, a noise may be caused by splashing the lubricatingoil 30, depending on a thickness, a material, or a shape of the hermeticshell 2 or a shape of cylinder block 5. However, in the second exemplaryembodiment, the selection of an adequate ratio G from the range of 0.25to 0.5 can set an amount of supplied oil appropriate for each number ofrevolutions in operation and prevent the noise problem caused bysplashing the lubricating oil 30 especially in the range of high-speedoperation.

Third Exemplary Embodiment

FIG. 9 is an enlarged sectional view of a lower portion of a maincrankshaft in accordance with the third exemplary embodiment of thepresent invention. FIG. 10 is a perspective view of a divider. FIG. 11is an enlarged sectional view of the D portion of FIG. 9.

An extended tubular part 18 is formed at the bottom of a main crankshaft7 a. The slanting channel 19 is a passage for lubricating an oilprovided from the top end of the extended tubular part 18. The innerdiameter of the slanting channel 19 includes the center of the extendedtubular part 18. A divider 26 is shaped like a thin flat plate that ispress-fitted into the slanting channel 19. The divider 26 has asemi-circular notch 27 at each of the top and bottom ends thereof. Thedivider 26 is formed symmetrically at the upper and lower sides so thatit can be inserted from any of top and bottom ends. The divider 26 has apress fit portion 28 in which substantially an intermediate portion ofthe divider is formed slightly wider. The diameter of the slantingchannel 19 is decreased stepwise at least once from the top end of theextended tubular part 18 so that the slanting channel has at least onestep. There is a step 19 b, a boundary between a first-step slantingchannel 19 a having the largest diameter in the slanting channel 19 anda second-step slanting channel. The first-step slanting channel 19 a isformed to be as high as divider 26.

The lubricating oil 30 that has flown into the slanting channel 19 movesupwardly while it rotates according to the rotation of the crankshaft 7.However, because the viscosity of the lubricating oil 30 serves as aresistance force against the rotation direction in the slanting channel19, the rotational speed of the lubricating oil 30 in the slantingchannel 19 tends to be smaller than the actual rotational speed of thecrankshaft 7. Especially in the range of low-speed operation (1,200 to1,800 rpm), the temperature rise of the lubricating oil 30 caused by theheat generated by the motor or a sliding is small and thus the viscosityof the lubricating oil 30 is kept relatively high. This makes a largedifference in a rotational speed between the lubricating oil 30 and thecrankshaft 7. Such a difference in rotational speed between thecrankshaft 7 and the lubricating oil 30 in the slanting channel 19largely affects and deteriorates an oil delivering force.

For the third exemplary embodiment of the present invention, the oildelivering force is improved by agitating up the lubricating oil 30 bystirring the divider 26 inserted into and engaged with the slantingchannel 19. Thus, the rotational speed of the lubricating oil 30 thathas flown into the slanting channel 19 is substantially the same as theactual rotational speed of the crankshaft 7 and sufficient oils islifted even in the range of low-speed operation.

Because substantially semi-circular notches 27 are provided at both endsof the divider 26, the ratio of two divided openings of the inlet portin the throttle 17 is kept unchanged even if the divider 26 is displacedfrom the center of the throttle 17. The divider 26 also has the pressfit portion 28 in which the width in the vicinity of the longitudinalcenter of the divider 26 is increased. The press fit portion 28 allowsan easy insertion and fixation of the divider 26. The divider 26 can beassembled without an extremely small bend. Thus, the workablity inassembling is improved.

Additionally, the diameter of the slanting channel 19 is decreasedstepwise at least once from the top end of the extended tubular part 18so that the slanting channel 19 has at least one step. The depth of thefirst-step slanting channel 19 a from the top end of the extendedtubular part 18 is equal to the height of the divider 26. When the cap31 is fitted into the extended tubular part 18, the cap 31 is broughtinto contact with the bottom end face of the divider 26 and a load maybe imposed on the divider. Even in such a case, the edge 26 a at the topend face of the divider 26 is restricted by the step 19 b of theslanting channel 19. This allows assembling without positioning divider26 by mistake.

Fourth Exemplary Embodiment

FIG. 12 is an enlarged sectional view of a top end portion of a slantingchannel in a main crankshaft in accordance with the fourth exemplaryembodiment of the present invention.

The main crankshaft 7 has the slanting channel 19, and a conical portion33 at the top end of the slanting channel 19. The conical portion 33 hasa ridge portion 33 a. Further provided is a lower communicating passage21 for further lifting the lubricating oil 30 in the slanting channel19.

Now, the slanting channel 19 inclines from the lower portion to theupper portion of the main crankshaft 7 toward the outer peripheral sideof the main crankshaft 7, in order to effectively lift up the head ofthe lubricating oil and ensure the amount of supplied oil in thelow-speed operation range. For this reason, when the lower communicatingpassage 21 is consisted to penetrate the side inner wall of the slantingchannel 19, the upper end portion of the slanting channel is the mostthinnest because the upper end portion of the slanting channel 19 andthe conical portion 33 are inevitably located above the lowercommunicating passage 21. Therefore, when a spiral groove (not shown) isformed upwardly from the lower communicating passage 21, a corrosion (aphenomenon of breakage at the lowest portion of the spiral groovedeveloping into a large hole that occurs in a thin portion) may occurbetween the lowest portion of the spiral groove 20, the upper end of theslanting channel 19, and conical portion 33.

However, in the fourth exemplary embodiment, the lower communicatingpassage 21 or a part thereof is formed of the ridge portion 33 a of theconical portion 33 at the top end of the slanting channel 19. Thus, inaddition to ensuring an amount of supplied oil in the range of low-speedoperation, a sufficient thickness is ensured in the portion above thelower communicating passage 21 of the main crankshaft 7. Therefore, evenwhen the spiral groove 20 is formed, a corrosion in this portion can beprevented and the loss in manufacturing cost can be reduced.

Fifth Exemplary Embodiment

FIG. 13 is an enlarged sectional view of a bearing for a main crankshaftin accordance with the fifth exemplary embodiment of the presentinvention.

In the crankshaft 7, the main crankshaft 7 a is supported by a bearing 8of a cylinder block. The rotor 3 b is shrink-fitted to the maincrankshaft 7 a. The main crankshaft 7 a has the slanting channel 19inside thereof. A vent communicating passage 25 for providing acommunication between the slanting channel 19 and the outer peripheralsurface of the crankshaft 7 a is provided in a position of clearance 34formed between the bottom end of the bearing 8 of the cylinder block andthe top end of the rotor 3 b.

In the fifth exemplary embodiment of the present invention, in order toprevent an insufficient lubrication phenomenon in which gas retained inthe slanting channel 19 causes a choke and hinders the lubricating oil30 from going up, the gas retained in the slanting channel 19 caneffectively be released from the vent communicating passage 25 throughthe clearance 34. Additionally, because the height from the oil sump tothe center of the vent communicating passage 25 is sufficiently ensured,the rate of the amount of lubricating oil flowing out of the ventcommunicating passage 25 is decreased. This can ensure an amount ofsupplied oil sufficient to contribute to lubricate the sliding parts.

At least a part of the vent communicating passage 25 in the fifthexemplary embodiment extends to the sliding part comprising the maincrankshaft 7 a and the bearing 8. Beveling an outlet port 25 a of thevent communicating passage 25 opened to the outer peripheral side of themain crankshaft 7 a can prevent a shortage of oil film on the journalbearings comprising the bearing 8 of the cylinder block and the outerperipheral surface of the main crankshaft 7 a.

Further, in order to release a gas from the slanting channel 19 andprevent a shortage of oil film on the journal bearing at the same time,it is desirable to set the diameter of the outlet port 25 a to 3 to 6 mmand the bevel angle to 90° to 120°.

INDUSTRIAL APPLICABILITY

As described above, the present invention includes an oil pump. The oilpump comprises: a slanting channel formed in the lower portion of a mainshaft and inclining from the lower portion to the upper portion thereofoutwardly; a throttle formed at the bottom of the main shaft and havingan inlet port of diameter smaller than the section of the slantingchannel; and a lower communicating passage for providing communicationbetween the bottom end of a spiral groove and the slanting channel. Thecentrifugal force resulting from a rotation of a crankshaft is exertedon lubricating oil at the bottom end of the main crankshaft surroundedby the throttle. The throttle receives the downward force generated bythe centrifugal force. This increases the upward force and allows thelubricating oil to move upwardly in the slanting channel. Further, theincline of the slanting channel effectively lifts the head of thelubricating oil to provide a large oil delivering force. This canrealize a hermetic electric compressor capable of efficiently pumping upthe lubricating oil required even at low speeds of rotation.

The present invention can also provide a hermetic electric compressorhaving a simple constitution and thus excellent workablity inassembling.

REFERENCE MARKS IN THE DRAWINGS

-   1 Hermetic electric compressor body-   2 Hermetically-sealed upper and lower shells-   3 Electric motor-   3 a Stator-   3 b Rotor-   4 Compressing mechanism-   5 Cylinder block-   6 Compressor unit-   7 Crankshaft-   7 a Main crankshaft-   7 b Eccentric crankshaft-   8 Bearing-   10 Connecting rod-   11 Piston pin-   12 Cylinder-   13 Piston-   14 Valve plate-   15 Cylinder head-   16 Suction muffler-   17 Throttle-   18 Extended tubular part-   19 Slanting channel-   19 a First step slanting channel-   19 b Step-   20 Spiral groove-   21 Lower communicating passage-   23 Through-hole-   24 Upper communicating passage-   25 Vent communicating passage-   25 a Outlet port-   26 Divider-   26 a Edge-   27 Notch-   28 Press fit portion-   29 Inlet port-   30 Lubricating oil-   31 Cap-   33 Conical portion-   33 a Ridge portion-   34 Clearance

1. A hermetic electric compressor comprising: an electric motorcomprising a stator and a rotor; a compressing element for compressingrefrigerant by a rotation of a crankshaft fixed to the rotor of saidelectric motor; a hermetic shell housing said electric motor and saidcompressing element and including a reservoir arranged to storelubricating oil, said crankshaft comprising at least a main crankshaft,and a eccentric crankshaft for driving said compressing element; an oilpump for supplying said lubricating oil in said reservoir to an insideof said hermetically-sealed shell by rotation of the crankshaft via saidmain crankshaft and said eccentric crankshaft by a rotation of saidcrankshaft, said oil pump being provided inside of said main crankshaft,and said oil pump comprising: a slanting channel having a predeterminedlength and provided from a bottom end of said main crankshaft, saidslanting channel slanting with respect to a center axis of said maincrankshaft, the bottom end of said main crankshaft arranged to beimmersed in said stored lubricating oil; a throttle provided at saidbottom end of said main crankshaft and having a cross-sectional areasmaller than a cross-sectional area that of said slanting channel; acommunicating passage provided at a top end of said slanting channel; aspiral groove in communication with said communicating passage, providedin an outer periphery of said main crankshaft; and a through-hole incommunication with said spiral groove, provided in said eccentriccrankshaft.
 2. The hermetic electric compressor of claim 1, wherein arevolution of said main shaft includes from 1,200 to 1,800 revolutionsper minute (rpm).
 3. The hermetic electric compressor of claim 1,wherein when a ratio of a distance from a bottom end of said maincrankshaft to a center of said communicating passage to a diameter ofsaid main crankshaft including said slanting channel is set to E, saidratio E ranges from 2 to 3, and when a ratio of a maximum length from acenter axis of said main crankshaft to an outer diameter of saidslanting channel to a half of the diameter of said main shaft is set toF, ratio E ranges from 2 to 3 and said ratio F ranges from 0.77 to 0.9.4. The hermetic electric compressor of claim 3, wherein a relationbetween said ratio E and said ratio F is shown by the followingequation:F0.166E ²−0.683E+1.44.
 5. The hermetic electric compressor of any one ofclaims 1 through 4, wherein said throttle is constituted so that adisk-shaped cap is inserted in and engaged with the bottom end of saidmain crankshaft.
 6. The hermetic electric compressor of any one ofclaims 1 through 4, wherein a ratio of a diameter of said slantingchannel to a diameter of the inlet port provided at the center of saidthrottle is set to 1:0.25 to 0.5.
 7. The hermetic electric compressor ofany one of claims 1 through 4, wherein a divider for dividing saidslanting channel is inserted in and engaged with said slanting channelabove said throttle.
 8. The hermetic electric compressor of claim 7,wherein said divider is shaped like a vertically symmetrical flat plate,said divider has substantially a semi-circular notch at a nearly centerof at least a bottom end thereof and a press fit portion, and in saidpress fit portion, a width of a longitudinal center of said divider islarger than a width of top and bottom ends.
 9. The hermetic electriccompressor of claim 7, wherein a step is provided in a position in adirection of a depth of said slanting channel, and a distance from abottom end of said slanting channel to said step is equal to a length ofsaid divider.
 10. The hermetic electric compressor of any one of claims1 through 4, wherein a conical portion is formed at the top end of saidslanting channel, and at least a part of said communicating passageintersects said conical portion.
 11. The hermetic electric compressor ofany one of claims 1 through 4, further comprising a vent communicatingpassage, said vent communicating passage providing a communicationbetween said slanting channel and an outer peripheral surface of saidmain crankshaft and being opened to a space in said hermetic shell.